Strain-engineering Mott-insulating La<sub>2</sub>CuO<sub>4</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30783084.
- Also identified by DOI 10.1038/s41467-019-08664-6 and PMC identifier 6381167.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The transition temperature T<sub>c</sub> of unconventional superconductivity is often tunable. For a monolayer of FeSe, for example, the sweet spot is uniquely bound to titanium-oxide substrates. By contrast for La<sub>2-x</sub>Sr<sub>x</sub>CuO<sub>4</sub> thin films, such substrates are sub-optimal and the highest T<sub>c</sub> is instead obtained using LaSrAlO<sub>4</sub>. An outstanding challenge is thus to understand the optimal conditions for superconductivity in thin films: which microscopic parameters drive the change in T<sub>c</sub> and how can we tune them? Here we demonstrate, by a combination of x-ray absorption and resonant inelastic x-ray scattering spectroscopy, how the Coulomb and magnetic-exchange interaction of La<sub>2</sub>CuO<sub>4</sub> thin films can be enhanced by compressive strain. Our experiments and theoretical calculations establish that the substrate producing the largest T<sub>c</sub> under doping also generates the largest nearest neighbour hopping integral, Coulomb and magnetic-exchange interaction. We hence suggest optimising the parent Mott state as a strategy for enhancing the superconducting transition temperature in cuprates.